1. Field of the Invention
The present invention relates to a cap device equipped with a tether mechanism for linking a cap used to open and close a tank opening to a peripheral member of the tank opening.
2. Description of the Related Art
In a fuel tank of automobiles, there is a known structure of linking a fuel cap to a peripheral member of a fuel inlet by means of a tether, in order to prevent the fuel cap from being lost during a fuel supply operation (see, for example, JP No. 2000-507192A). FIG. 8 shows a tether mechanism 100 of a prior art structure. The tether mechanism 100 includes a rotating ring 102 that is mounted in a freely rotatable manner on an outer circumference of a fuel cap (not shown), and a linkage member 110 with one end connected to the rotating ring 102 and the other end linked to a vehicle body. The rotating ring 102 and the linkage member 110 are made of a resin. The linkage member 110 is integrally formed and has a cord-like linkage body 112 and a support end 114 that is protruded from one end of the linkage body 112. The rotating ring 102 has a ring body 104 and a support member 106 that is formed as part of the ring body 104 to engage with the support end 114. The support member 106 has a support recess 106a that is open to the inner circumference of the ring body 104, an insertion opening 106b that is open upward the support recess 106a, and a lead opening 106c that is open outward in a radial direction of the support recess 106a. 
The support end 114 of the linkage member 110 is fixed to the support member 106 of the rotating ring 102 according to the following procedure. The linkage body 112 is pressed into the insertion opening 106b in the direction of an arrow D1, and the support end 114 is pressed into the support recess 106a in the direction of an arrow D2. This fits the support end 114 in the support recess 106a, while enabling the linkage body 112 from being pulled through the lead opening 106c. The rotating ring 102 integrated with the linkage member 110 is then attached to the outer circumference of the fuel cap.
This fixation process requires the actions in the two different directions, that is, press-in of the linkage member 110 in the direction of the arrow D1 and in the direction of the arrow D2. There is a difficulty in automating such actions in the two different directions, since secure support of the linkage member 110 of flexible resin is demanded during the fixation. The press-in of the linkage body 112 into the narrow insertion opening 106b may result in breakage of the linkage body 112.